Not applicable.
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The field of the invention is mechanical bridges and more specifically bridges including spans that are openable.
Bridges are required to facilitate convenient rail and vehicular traffic over rivers, streams, dams and the like (hereinafter collectively referred to as rivers). While bridges are necessary, unfortunately bridges can impede passage of vessels along rivers there below. In order to accommodate both rail and vehicular traffic over rivers and travel along the rivers by ships, barges, etc, bridge designers have developed several different mechanical type bridges including one or more bridge spans that can open and close.
One mechanical bridge type is generally referred to as a vertical-lift bridge. A vertical-lift bridge typically includes vertical towers at either end of a bridge span. When positioned for vehicular traffic, the span is in a low position where a top surface is aligned with top surfaces of adjacent bridge spans. To accommodate travel below the bridge span the span can be raised between the towers.
While vertical-lift bridges can accommodate both river and vehicular travel, these bridges have several shortcomings. First, vertical-lift bridges, while accommodating some river travel, still restrict travel as the lifted span remains above the area through which travel occurs. Second, the motors and other mechanical equipment required to lift the bridge span are relatively large and therefore expensive. In addition, because of the mechanics involved with vertical-lift bridges, maintenance costs for vertical lift bridges are relatively high.
Another mechanical bridge type is a swing span bridge. A typical swing span bridge includes a moveable span that pivots about a vertical axis to provide required opening clearance for navigation traffic. Swing spans are typically symmetrical with equal length cantilevers to each side of the vertical axis. Some swing span bridges, however, are configured with unsymmetrical cantilevers that are counterweighted to balance the bridge. Swing span bridges are advantageous as they provide unlimited vertical clearance for river bound traffic when the span is open.
Unfortunately swing spans also have several shortcomings. First, when a swing span is horizontally pivoted into the open position the span ends are generally considered to be navigational hazards. The span ends are directed against movement of water bound traffic and therefore are prone to vessel collision. Thus, often substantial fender systems are required to protect the span and vessels in the area. Second, swing spans typically require twice as much moveable length span as other mechanical span designs to provide the same opening width. This is because, as indicated above, most swing span bridges require equal length span segments cantilevered about the vertical pivot point. Third, the mechanical components required to manipulate the large span sections are generally relatively large and therefore relatively expensive.
Yet one other mechanical bridge type is referred to generally as a bascule type bridge. A typical bascule bridge includes a leaf that pivots about a horizontal axis to provide a required opening and clearance for river bound traffic. Counterweights are usually provided to balance the weight of the span and minimize the operating requirements on the drive machinery. The bascule span bridges provide unlimited vertical clearance when open.
Bascule bridges, like the other bridge types described above, have several shortcomings. First, the counterweight required to balance the bascule span is typically rather large. As most mechanical bridges are relatively low to the water, the counterweights are typically positioned above a span adjacent the moveable span. To support the counterweight these bridge types often require large and expensive overhead framing systems and massive foundations below the spans to handle the overturning moments that occur. Second, the mechanics required to control a bascule bridge are extremely complex and therefore expensive. Third, bascule bridges requiring massive counterweights are relatively unsafe in certain geographic areas that are subject to seismic tremors.
Thus, there is a need for a mechanical bridge that is simple, relatively inexpensive, provides unlimited vertical clearance and that does not require massive overhead or counterweight components.
It has been recognized that a relatively simple bridge design can overcome many of the shortcomings of the prior art bridges described above. To this end, by moving a bridge span essentially within a single vertical plane from a supporting position into a storage position, system mechanics can be greatly simplified without sacrificing safety. To this end, in one embodiment, an openable span is moved laterally from a supporting position and then longitudinally along the side of an adjacent span to open a space for water bound traffic. In another embodiment an adjacent span is removed from its position adjacent an openable span and then the openable span is moved at least in part into the adjacent position to open a space for water bound traffic.
Thus, one object of the invention is to provide a simplified openable bridge design. This object is accomplished by minimizing required vertical span movement. In some embodiments there is no vertical span movement while in other embodiments vertical movement is limited in several ways. First, the vertical distance of movement is minimized. Second the size of the span that has to be moved is limited. To this end, when a first span is vertically moved and then a second span is horizontally moved into the space originally occupied by the first span, the first span is only half as large as the second span and hence a minimally sized span is vertically moved.
Another object is to provide a relatively safe mechanical bridge. To this end, because vertical span movement is limited, above deck structure is minimized. Because above deck structure is minimized bridges constructed according to the present teachings are relatively safe in various environments including those that may be subject to periodic earth quakes and other disruptive natural phenomenon.
Yet one other object is to provide a relatively inexpensive bridge system. Because most span movement is horizontal relatively small motors can be used to move spans on rollers as opposed to lifting the spans.
One other object is to provide a bridge where, when a span is open, the open space can accommodate passage of any vessel there below. To this end the present design has no components that remain above the open space after a span is moved.
Consistent with the above objects and advantages, the present invention includes a bridge assembly comprising first, second and third adjacent piers, the first and second piers defining a first space there between and the second and third piers defining a second space there between, third and fourth spaces above the first and second spaces, respectively, a first bridge span positionable so as to traverse the distance between the first and second piers within the third space, a second bridge span positionable so as to traverse the distance between the second and third piers within the fourth space, a first motivator linked to the first bridge span for moving the first span into and out of the third space and a second motivator linked to the second bridge span for moving at least a portion of the second bridge span from the fourth space to the third space so that at least a portion of the fourth space is unobstructed.
In some embodiments the invention further includes at least one intermediate pier between the second and third piers, the space between the intermediate and third piers being a fifth space, the space above the fifth space being an openable space, the openable space being the portion of the fourth space that is unobstructed when the portion of the second bridge span is moved to the third space. In some cases the first, second, third and intermediate piers are essentially equi-spaced.
In some embodiments roller members are provided between the tops of the piers and the spans thereabove. The rollers may be mounted to the tops of the piers.
In several embodiments the first span has a span width, each of the first and second piers has a pier width that is substantially twice as wide as the span width, first and second in-line sections of the first and second piers, respectively, aligned with the third pier and defining an in-line space, a supporting space above the in-line space, first and second lateral sections of the first and second piers laterally adjacent the first and second in-line sections, respectively, the lateral sections defining a lateral space there between, a receiving space above the lateral space, the first motivator for moving the first span between the supporting space and the receiving space.
In some embodiments the first and second in-line sections and first and second lateral sections comprise one lateral load bearing element and the first span comprises another lateral load bearing element and the assembly further includes a first track mounted to a first one of the lateral load bearing elements and rollers mounted to the second of the lateral load bearing elements, the rollers supportable on the track to facilitate rolling of the first span between the supporting and receiving spaces. Here, the track may be secured to the first span and the rollers may be secured to the tops of the piers.
The assembly may further include an intermediate pier between the second and third piers wherein the second and intermediate piers comprise a longitudinal load bearing element and the second span comprises another longitudinal load bearing element and, wherein, the assembly further includes a second track mounted to a first one of the longitudinal load bearing elements and rollers mounted to the second of the longitudinal load bearing elements, the rollers supportable on the track to facilitate rolling of the second span such that the at least one section moves between the fourth space and the supporting space. The longitudinal load bearing element that includes the second and fourth piers may also includes the first pier.
In some embodiments the first motivator moves the first span between the third space and a space above the third space. In other embodiments the first motivator moves the first span between the third space and the first space.
The second span may include first and second ends, a top and a bottom, the second end adjacent the third pier when the second span is in the fourth space, the assembly further including first and second aligning apparatus at the second end and the top of the third pier, respectively, the second aligning apparatus receiving the first aligning apparatus when the second span is moved into the fourth space so as to align the second span with the third pier. The first aligning apparatus may include a first inclined surface. Similarly, the second aligning apparatus may include a second inclined surface. In addition, the second aligning apparatus may include a guiding roller.
Another embodiment of the invention includes a method for opening a section of a bridge where the bridge includes several spans that are longitudinally arranged along the length of the bridge including at least first and second adjacent spans that, when the bridge is closed, occupy first and second spaces, respectively, the method comprising the steps of moving the first bridge span from the first space, moving at least a segment of the second bridge span from the second space into the first space so that at least a portion of the second space is unobstructed.
According to one embodiment, when the first span is in the first space and the second span is in the second space the first and second spans are aligned longitudinally and, the step of moving the first bridge span includes moving the first span from the first space laterally and wherein the step of moving the second span includes moving the second span longitudinally. In another embodiment, the step of moving the first bridge span includes moving the first span upward and out of the first space.
In yet another embodiment the invention includes a bridge assembly comprising first, second and third adjacent piers, each of the second and third piers including an in-line section and an adjacent lateral section, the in-line sections aligned along a longitudinal axis and the lateral sections aligned along a lateral axis that is essentially parallel to the longitudinal axis, the first pier and second pier in-line section defining a first in-line space there between, the second and third pier in-line sections defining a second in-line space there between, a space adjacent the first in-line space and the second lateral section defining a first lateral space, the second and third lateral sections defining a second lateral space there between, third and fourth in-line spaces above the first and second in-line spaces, respectively, and third and fourth lateral spaces above the first and second lateral spaces, respectively, a first bridge span positioned so as to traverse the distance between the first and second piers within the third in-line space, a second bridge span positionable so as to traverse the distance between the second and third piers within the fourth in-line space, a first motivator linkable to the second bridge span for moving the second span between the fourth in-line space and the fourth lateral space and a second motivator linkable to the second bridge span for moving at least a portion of the second bridge span from the fourth lateral space to the third lateral space so that at least a portion of the fourth lateral space is unobstructed.
Here the assembly may further include at least one intermediate pier between the second and third lateral pier sections, the space between the intermediate and third lateral section being a fifth space, the space above the fifth space being an openable space, the openable space being the portion of the fourth lateral space that is unobstructed when the portion of the second bridge span is moved to the third lateral space. The first lateral section, second lateral section, third lateral section and intermediate pier may be essentially equi-spaced.
The invention further includes a method for opening a section of a bridge where the bridge includes at least first and second adjacent spans that are longitudinally alignable along the length of the bridge and are supported by at least first, second and third piers, each pier including an in-line section and a lateral section laterally positioned with respect to the in-line section, the space between the first and second in-line pier sections being a first in-line space, the space between the second and third in-line pier sections being a second in-line space, the space above the first and second in-line spaces being a third in-line space and the space above the second in-line space being a fourth in-line space, the space between the first and second lateral pier sections being a first lateral space, the space between the second and third lateral pier sections being a second lateral space, the space above the first lateral space being a third lateral space and the space above the second lateral space being a fourth lateral space, when the bridge is closed, the first and second spans occupying the third and fourth in-line spaces, respectively, the method comprising the steps of: moving the second bridge span laterally from the fourth in-line space to the fourth lateral space and moving at least a segment of the second bridge span from the fourth lateral space into the third lateral space so that at least a portion of the fourth space and a portion of the fourth lateral space are unobstructed.
These and other objects, advantages and aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefor, to the claims herein for interpreting the scope of the invention.